At the present time, a user is able to control the execution of a function of a vehicle by means of a mobile apparatus, for example a smartphone. The function in question is, for example, one of the following functions: locking/unlocking the vehicle, starting the vehicle, automatic parking, etc. In some applications, in order to be able to execute one of these functions, the mobile apparatus must have previously stored an identification key authorizing the execution of at least one function of the vehicle. The identification key is stored in a secure element of the mobile apparatus, for example its SIM card. By keeping the mobile apparatus with him, the user can thus, for example, unlock the lock of an openable body section of the vehicle. For this purpose, data, notably authentication data contained in the identification key, are exchanged between the mobile apparatus and an electronic module of the vehicle, which determines whether the vehicle's identification key is valid. In advantageous embodiments, these data exchanges are carried out in accordance with the BLE (Bluetooth Low Energy) protocol.
For reasons of safety, the execution of a function of the vehicle is dependent on the location of the mobile apparatus with respect to the vehicle. The vehicle may be unlocked when the user, and therefore the mobile apparatus, are located near the vehicle, at a distance of about 50 cm. However, the user must still demonstrate his intention of unlocking the vehicle by actuating a handle of the vehicle to enable the vehicle's unlocking function to be executed. Similarly, the vehicle is locked, provided that the openable body sections are closed, when the user moves away from the vehicle, for example over a distance of more than one or two meters. It may therefore be assumed that the vehicle is locked while it is still in the field of view of the user, thus preventing any malicious intrusion when the user can no longer see his vehicle. Finally, for the purpose of starting the vehicle, the mobile apparatus must be inside the passenger compartment.
Various solutions are currently used to measure the distance between the mobile apparatus and the vehicle, for example measuring the power of a received signal whose initial power is known, enabling the distance between the transmitter and the receiver to be deduced. This method is known as “measurement by RSSI”, an abbreviation for Received Signal Strength Indication in English. Another solution consists in measurement by GPS, or alternatively, for example in locations where GPS is not accessible, measurement using the data supplied by the gyroscopic and accelerometric sensors of the mobile apparatus. The mobile apparatus uses these data for calculating and recording the user's movements. This method is known as “true positioning” in English.
Measurements by RSSI and GPS are imprecise, with errors of the order of several meters, and therefore do not ensure compliance with the specifications for making the activation of the functions of the vehicle dependent on the position of the mobile apparatus with respect to the vehicle. Furthermore, it is desirable to operate without using the gyroscopic sensors and acceleration sensors of the mobile apparatus, thus avoiding the use of true positioning.